1. Field of the Invention
This invention relates in general to digital to analog converters for conversion of digital-analog signals.
2. Description of the Prior Art
It is known in digital-analog converters of the type specified for example, in "Elektronik-Praxis", No. 1/2, February 1975, pages 32ff to provide a logarithmic companding characteristic line which corresponds to the CCITT recommendation and operates according to the so-called A-law which utilizes non-linear steep-drop characteristic curves.
Companding according to such a characteristic curve in the analog-digital conversion or corresponding digital to analog conversion is required so as to assure that the ratio of the analog signal amplitude to the interference voltage amplitude caused by the quantization of the analog signal is approximately constant over a wide analog signal amplitude range.
In addition to the logarithmic characteristic curve which follows the A-law, the CCITT recommends a further logarithmic characteristic curve which obeys the so-called .mu.-law. Although the characteristic curve obeying the A-law can be approached in a particularly favorable manner in terms of circuitry by means of a non-linear steep-drop characteristic curve the .mu.-characteristic curve is preferred in certain countries.